Manufacturers measure their own MTF charts, and it is normally a computer generated estimate, just like MPG figures for new cars. Further, you can't compare MTF graphs within manufacturers if the focal lengths differ much, the only thing you can really glean from manufacturer supplied MTF charts is how good, or bad, they are compared to an earlier version.

Thank you, I didn't know.

Than we can only assume that it's definitely better than its predecessor. Will be nice to see how it behaves on the D800.

Manufacturers measure their own MTF charts, and it is normally a computer generated estimate, just like MPG figures for new cars. Further, you can't compare MTF graphs within manufacturers if the focal lengths differ much, the only thing you can really glean from manufacturer supplied MTF charts is how good, or bad, they are compared to an earlier version.

This isn't really true. MTF data is generated from theoretical data which would be the same for any lens built perfectly (ie no copy variation or manufacturing tolerances). You can compre MTF data between manufacturers if you know HOW to compare it and how to read the chart.

The Nikon 80-400 should be as good as the Canon 24-70 ii 2.8.

Copy variation and manufacturing tolerances do play a role though in the end result but those should cancel out more or less between manufacturers.

If all manufacturers used exactly the same model and computer program, maybe, but they don't. You can understand it all, it isn't that difficult ( http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml ), but unless the graphs are drawn from the same testing equipment using actual lenses MTF graphs are very limited in value. As for manufacturer supplied figures, don't forget it is the sales department that is showing you this stuff

Manufacturers MTF curves are accurate enough, but they are for the lens, and not for a lens-camera combination. So far, all the online lens reviewers including DXO do not measure lens MTF. They measure a combination camera body - lens MTF which will always be poorer. Lots of factors enter into this, but you can never achieve the lens mtf when its on a camera body because the camera body degrades the image significantly.

With film bodies, the film had a MTF as well, and degraded the image. MTF's were published for cinema film.

I wouldn't consider the 100-400L as good as the Canon 24-70 f/2.8 II, and I will certainly be shocked if this new 80-400 is that good.

At f/8, it is very good. I don't think it is up to the 24-70 f/2.8 II. Wide open, it isn't that close. Still, good, but the 24-70 f/2.8 II starts in the >0.9 range even wide open. The 80-400 is around 0.85 to 0.87 range. Close, but not "as good" in either instance.

But I do think it is a fair point that there will be differences between Canon and Nikon.

Accurate enough for what? They could well be derived from completely different methods, so the one thing you can't do is accurately compare between manufacturers. You also can't compare different focal lengths! So whilst manufacturer presented MTF graphs might be "accurate enough", I was just adding a cautionary note to those who were comparing Nikon figures to Canon figures. Just like MPG estimates, they have very limited value and shouldn't be a serious basis for a purchase.

Lensrentals now has the equipment to measure lens resolution without being mounted (to a camera as we know it) so they can, at least, give genuine comparisons for lenses across manufacturers.

MTF is definitely not the final word, but its a starting point, and a lens is not going to be better than the manufacturers posted MTF. The values that the camera manufacturers are good enough precisely because of this, there is no use being accurate to 5 or 10%% because it is only part of the story.

Do you have a link to Rogers optical bench and colliminator? as well as the PHD's he has hired to run it? The last time I saw any information was that he used Imatest like all the other testers.

Measuring the MTF of a lens with a optical bench, slit illuminator, not only takes 500K of equipment, but also needs some very skilled technicians to intrepret the results. I had all of those in my lab at a large aerospace company, and it was a big investment assembled over several years of R&D budget. We had several lab techs and engineers / scientists using it. Its not something easily done.

Somehow, I wonder if Roger has acquired this ability, or even why he would want to, since Imatest is plenty good for what he does. But please give me a link and impress me.

"Do you have a link to Rogers optical bench and colliminator? as well as the PHD's he has hired to run it? The last time I saw any information was that he used Imatest like all the other testers."

No. But you need to read him more clearly, he often says things like "A lot of my posts about lens resolution consist largely of showing the MTF 50 numbers from Imatest or our optical bench." and "I grew up in biological and medical research ".

It's a Well's OS-400 system, modified by Wells to take interchangeable mount lenses. We didn't hire any Ph. D.s, but had one come teach us how to use it. As mentioned above, it's not the be-all-end-all but it compliments Imatest nicely. Imatest's greatest shortcoming is it can't measure lenses at infinity and the optical bench does. Imatest does some other things much better than the optical bench, though.

And it's certainly not up to aerospace standards, this is a lower end (albeit still near 6 figures) system, but it does give use some really nice information, particularly regarding astigmatism and frequency response that Imatest just can't provide.

"Do you have a link to Rogers optical bench and colliminator? as well as the PHD's he has hired to run it? The last time I saw any information was that he used Imatest like all the other testers."

No. But you need to read him more clearly, he often says things like "A lot of my posts about lens resolution consist largely of showing the MTF 50 numbers from Imatest or our optical bench." and "I grew up in biological and medical research ".

It's a Well's OS-400 system, modified by Wells to take interchangeable mount lenses. We didn't hire any Ph. D.s, but had one come teach us how to use it. As mentioned above, it's not the be-all-end-all but it compliments Imatest nicely. Imatest's greatest shortcoming is it can't measure lenses at infinity and the optical bench does. Imatest does some other things much better than the optical bench, though.

And it's certainly not up to aerospace standards, this is a lower end (albeit still near 6 figures) system, but it does give use some really nice information, particularly regarding astigmatism and frequency response that Imatest just can't provide.

Thanks Roger, I am impressed! I've seen the Wells systems online before, but you are the first I've heard of using one that wasn't a large corporation, or a R&D or educational institution.

The system we used was partially home made, a 5 X 10 foot slab of 4 inch thick Aluminum plate, that was milled flat and drilled to mount the fixtures. It also had a expensive shock isolation system to help dampen very low frequency vibrations. Our techs milled custom fixtures for us as needed for different applications, but we also bought some of the standard components. We used it for research on military and space applications. I'd love to have one to play with.